Just realised a potential problem with Pass2U. It converts barcodes into QR codes (which I believe is a requirement for Wallet). If the merchant's barcode scanner isn't programmed to support QR codes (in which case, what year is this?) then it's pretty much useless.
Edit: Actually it doesn't, I'm completely wrong!
Edit again: One of my barcodes just converted to a QR code, by itself.